Radio receiving set



Jan. 19, 1937. A. N. GOLDSMITH RADIO RECEIVING SET Filed Nov; 12, 1930' ULTKA SELECT/V5 19/6/1' flUAL/T Y INVENTOR 15 ALFRED N. GOLDSMITH BY 1 g ATTORNEY Patented Jan. 19, 1937 UNITED STATES PATENT OFFICE 18 Claims.

The present invention relates to the art of radio receivers, and is more particularly a continuation in part of my copending application Serial No. 225,083 filed October 10, 1927, dealing with a radio receiving set designed. both for exceptionally high quality and ultra-selectivereception.

In view of the narrow band of frequencies sep- I arating the various broadcasting stations in the sharp tuning, the tone quality of reception is somewhat reduced.

It is therefore an object of this inventionto provide aradio receiving set which is of a highly selective character, but which does not sacrifice the quality of signal reception. .1.

It is a further object of this invention to produce a radio receiving set which may be operated as an ultra-selective and relatively lower quality set, and, alternatively,,asa relatively less selective, but relatively, higher quality receiver.

It is a further object of this invention to, provide a radio receiving set which may be changed readily to provide'either ultra or extreme selectivity and relatively poorer quality, or relatively lower selectivity and relatively higher quality.

And finally it is a further object of this invention to provide aradio receiving set which may be adjusted selectively, and at the will of the operator, to give any particular combination of tone quality and selectivity.

The novel features which I believe to be characteristic of my invention are set forth in particularity in the appended claims, the invention itself, however, as to both its organization and method of operation will best be understood by reference to the following description taken in connection with the drawing in which I have indicated diagrammatically several circuit organizations whereby my invention may be carried into effect.

In the drawing,

Fig. 1 diagrammatically shows one embodiment of the invention,

Fig. 2 shows a modified form of the invention,

Fig. 3 is still another modification of the invention. 1

Referring to the drawing wherein like characters of reference designate the same elements in the difierent figures, the antenna in Fig. 1 is shown at A, and to this is coupled an electron discharge tube H which serves as the first stage of radio frequency amplification. The input circuit of the tube H is provided with the tuned circuit 22,13 in a manner well understood in connection with tuned radio frequency receivers. The tube Ha is coupled to the tube It, and provides an additional stageof radio frequency amplification. 1 Obviously, the number of stages of radio frequency amplification may be varied as found desirable. The tube Ha is provided with the tuned circuit i2a, l3a, this tuned circuit being similar to the tuned circuit of the tube II described above. The usual battery connections are provided, and need no further explanation here. The output of the last radio frequency amplifying tube i I a may be coupled to the next stage, for example a detector, in the usual manner.

In, accordance with this invention variable capacities C1 and C2, which may be of any suitable form, are connected in the input circuits of the amplifier tubes i! and Ila. A connecting link l5 joins the movable elements of the capacities so that all of them may be varied simultaneously by one manual operation. A pointer I6 may be mounted upon the link l5, which pointer is made to move over a fixed scale ll to indicate the adjustment of the capacities. Iffcund desirable, the separate capacities may be arranged so that each may be independently varied to provide any desired adjustment. M

It will, be noted that the capacities C1 and C2 are represented as variable in difierent directions, the arrows in each caserepresenting that the capacity is to be increased when the other is decreased and vice versa. The mechanical coupling between the common actuator 15 and the capacities C1 and C2 can be of any desired arrangement, the sole requisite of design being that the capacities be inversely related with respect to their variation.

Thus, after the tuning condensers 13, Ha (connected for conventional uni-control by dotted lines 28) have been adjusted to a desired tuning setting, a predetermined amount of detuning is provided in each tube circuit, in the correct direction, by the single adjusting member l6. Movement of the pointer I6 to the left will provide sharp tuning, movement to the right will provide broad tuning. In order to broaden the tuning at a given setting of the rotors of condensers l3 and Hot, it is necessary to detune one of the tube circuits in one direction, and the other in the opposite direction.

The operation of the device, then, is as follows:

When the pointer 16 is moved to the extreme left hand position viewing Fig. 1 of the drawing, the capacities C1 and C2 are equal in value. Under'these conditions the circuits are all tuned alike, and the receiver is ultra-selective and will permit only a narrow band of frequencies to be amplified. In fact the arrangement is so highly selective that the tone quality is appreciably altered by reduction of high frequency tones. This adjustment is used only when maximum selectivity is required. If, however, fidelity is the desideratum and great selectivity is not required (a condition usually holding when local stations are being received), the pointer I 6 is moved to the right. This causes the capacities C1 and C2 to vary in opposite sense, thus detuning the input circuits of the amplifier tubes sufficiently to permit a wider band of frequencies to be reproduced with the consequent improvement in tone quality, while maintaining the frequency of the center of the selected band of fre quencies unchanged as the band is widened by adjustment of pointer I8.

Obviously, in the operation of aset embodying this invention it will not be necessary to operate the receiver exclusively at one or the other of the extreme positions of pointer I6. On the contrary, various adjustments of the pointer may be made to give various compromises between selectivity and high t'one quality. For reception of distant stations through local stations operating at nearby frequencies, the pointer would be adjusted until the set is just selective enough to avoid interference. This would insure the best tone quality permissible under the given conditions. Conversely, when receiving under conditions which require relatively less selectivity the tone quality may be improved by adjustment of the pointer to the right as far as might be permissible.

The herein described method of controlling the tone of a receiver is to be carefully distinguished from the method wherein the circuits of a receiver have been slightly detuned by adjustments of the variable condensers which form part of the normal tuning means, because when gang control is used the latter method does not broaden the tuning, as all the circuits are then detuned in the same direction by varying the tuning adjustment. This merely shifts the resonance point of the system from one carrier frequency to another. Where, however, as in the present method, one of the circuits is detuned slightly to one side of the selected carrier frequency to be received, and the other is detuned slightly in the opposite direction, the effect is to broaden the resonance curve of the selected carrier.

In Fig. 2 there is shown a modified form of the invention wherein the capacities C1 and C2 are replaced by adjustable inductances L1 and L2. Each inductance is provided with a plurality of closely spaced taps 2| and 2| respectively. The group of taps Z! is adapted for slidable contact with a movable arm 22, while a second arm 22' contacts with taps 2|. Each arm is electrically connected with the cathode, and mechanically coupled together by link I5, as in Fig. 1. The inductances are varied in value in an inverse manner, as described in connection with Fig. 1, the operation being similar with respect to broadening the tuning.

In Fig. 3, there is shown a modification wherein combined inductance and capacity elements are employed. In this case, for maximum selectivity the values of inserted inductive and condensive reactance are both zero, while for broadening of tuning, increasingly large values of the reactances are simultaneously inserted in the circuits. Thus, when the pointer I6 is displaced to one side the inductance and capacity L1 and 02 will broaden the tuning at a given setting, without changing the mid-frequency of the selected band.

The present invention should also be distinguished from methods known in the art which achieve improved fidelity by designing the various stages to remain always out of tune with each other, thus obtaining a band selecting characteristic, but not allowing the user of the set to adjust the width of band at will so as to make the most suitable choice between fidelity and selectivity for the particular station to which he is listening.

While the present invention has been disclosed specifically as applied to a tuned radio frequency receiver, it is to be understoodthat this invention is not limited to any particular type of re-' ceiving circuit. For example, the present ln-- vention is applicable to the intermediate ire-'- quency amplifiers of a superheterodyne receiver. In fact the invention is applicable to any receiving set which employs radio frequency amplification and/or amplification of super-audible frequencies. It is therefore to be understood that the terms radio frequency and superaudible frequency are used interchangeably throughoutthis specification and the claims.

While I have indicated and described several systems for carrying my invention into effect, it will be apparent to one skilled in the art that my invention is by no means limited to the particular organizations shown and described, but that many modifications may be made without departing from the scope ofmy invention as set forth in the appended claims. a

What I claim is:

1. A radio receiving set comprising a plurality of stages of amplification of superaudible frequencies, eachof said stages being provided with a tuned input circuit, a reactance disposed in each of said input circuits, and connected to the tuning means in each of said circuits, and means to simultaneously vary the said reactances in an inverse manner to detune each of said circuits while maintaining the mid-frequency of the selected band of frequencies substantially constant.

2. A radio receiving setcomprising a plurality of stages of amplification of super-audible frequencies, each of said stages being provided with an input circuit including a tuning condenser, an impedance element connected in each of said input circuits to its tuning condenser, means for varying selectively: each of said impedance elements to detune each of said input circuits in an inverse manner and a single means for simultaneously operating said last mentioned means.

3. A radio receiving set comprising a plurality of stages of radio frequency amplification, each of said stages being provided with an input circuit including a tuning condenser, means for adjusting the tuning condensers in each input circuit to a predetermined carrier frequency, and additional means in each of said input circuits to detune said inputcircuits in an inverse manner to broaden the resonance curve of said selected frequency.

4. A radio receiving set comprising at least two stages of superaudible frequency amplification, each stage being provided with an input circuit, a tuning means in each of said input circuits, a variable capacity in each input circuit, and means for simultaneously varying said capacities to detune said input circuits in an inverse manner.

5. A radio receiving set comprising at least two stages of superaudible frequency amplification, each stage being provided with an input circuit, a tuning means in each of said input circuits, a variable inductance in each input circuit, and means for simultaneously varying said inductances to detune said input circuits in an inverse manner.

6. A radio receiving set comprising at least two stages of superaudible frequency amplification, each stage being provided with an input circuit, a tuning means in each of said input circuits, an adjustable inductance disposed in one of said input circuits and connected to the tuning means of said input circuit, an adjustable capacity disposed in the input circuit of the other stage and connected to its tuning means, and means for simultaneously adjusting said inductance and capacity todetune the said input circuits in an inverse manner.

'7. A radio receiving set comprising a plurality of stages of radio frequency amplification, each of said stages being provided with an input circuit including a tuning reactor, means for adjusting the tuning reactors in each input circuit to a predetermined carrier frequency, and additional means in each of said input circuits to detune said input circuits in an inverse manner to broaden the resonance curve of said selected frequency.

8. In combination, in a high frequency system a source of high frequency energy, an output circuit, a network connected between said source and said output circuit and comprising at least two cascaded oscillation circuits each including a tuning reactor, uni-control means for adjusting the tuning reactors to a predetermined high frequency, and additional means in each of said oscillation circuits to detune said oscillation circuits in an inverse manner to broaden the resonance curve of said predetermined high frequency.

9. In a radio receiver, a multi-stage amplifier, each stage including a tube having a isingle resonant input circuit comprising a pair of reactances of opposite sign, means for simultaneously varying the reactances of the same sign to tune the multi-stage amplifier to a desired resonant frequency, and means for varying the form of the resonant curve of said amplifier at its resonant frequency while maintaining its resonant frequency substantially constant.

10. In a radio receiver, a multi-stage amplifier, each stage including a tube having a single resonant input circuit comprising a pair of reactances of opposite sign, the input circuits being tuned to a desired resonant frequency, and additional means in each output circuit for varying the Width of the resonance curve of said amplifier at its resonant peak while maintaining its resonant frequency substantially constant.

11. Radio communication apparatus comprising a plurality of coupled vacuum tube stages, each stage comprising a single tuned circuit which includes an inductive reactance and a capacitive reactance, said circuits being resonant to a common frequency, an auxiliary adjustable reactance in each circuit, and means for adjusting said auxiliary reactances to vary the sharpness of tuning of said high frequency circuits while maintaining the resonant frequency of said circuits substantially constant.

12. In a radio receiving set, a plurality of coupled vacuum tube stages, each stage comprising a single tuned circuit which includes an inductive reactance and a capacitive reactance, said circuits being resonant to a common frequency, said capacitative reactances being variable totune said circuits through a frequency range, auxiliary adjustable reactances, and means for simultaneously adjusting said auxiliary reactances to vary the width of the resonance peaks of the over-all. resonance curve of said circuits while maintaining substantially constant the resonance frequency of said radio receiving set.

13. In radio communication apparatus a plurality of coupled vacuum tube stages, each stage comprising a single tuned circuit which includes an inductive reactance and a capacitive reactance, means for adjusting said circuits to a common resonant frequency, auxiliary adjustable reactances, a common control for said auxiliary reactances, and means for varying the sharpness of tuning of said cascade circuits in an inverse manner by adjustment of said common control.

14. Radio receiving apparatus comprising a plurality of amplifying stages, means in said amplifying stages for varying the frequency to which said receiver is tuned, a pair of reactors, means connecting said reactors for simultaneous movement, but adjustment in opposite directions whereby the reactance of one of said reactors increases as the reactance'of the other reactor decreases, and connections electrically associating said reactors with said stages for varying the sharpness of tuning of said radio receiver while maintaining substantially constant the frequency to which it is tuned.

15. The method of varying the sharpness of tuning of a radio receiving set including a plurality of tuned circuits which comprises increasing the reactance in one of said tuned circuits, simultaneously decreasing the reactance of like nature in another tuned circuit, and co-ordinating the increase and decrease of reactance so that the sharpness of the resonance peak of the receiving set is varied while maintaining substantially constant the resonant frequency.

16. In combination with a pair of coupled tuned circuits, means including auxiliary reactances for increasing the natural frequency of one circuit by a small amount and decreasing the natural frequency of the other circuit by approximately the same amount.

17. In a superheterodyne receiver, a tuned intermediate frequency amplifier employing two coupled tunable circuits, auxiliary reactances in the said coupled circuits and a single control switch for increasing the natural frequency of one of the circuits by a given amount, and decreasing the natural frequency of the other circuit by approximately the same amount.

18. In a superheterodyne receiver having a tuned intermediate frequency amplifier, said amplifier using coupled tunable circuits, a single control switching arrangement which serves practically to instantaneously change the electrical characteristics of the two circuits so that the tuned frequency of one circuit is increased by a given amount and the tuned frequency of the other circuit is lowered by approximately the same amount.

ALFRED N. GOLDSMITH. 

